Switchable Valve Lifter Having a Mis-Assembly Indicator

ABSTRACT

An improved SHVL for an internal combustion engine comprises an improved arrangement for locking a spring tower into a pin housing. The spring tower is provided with an annular OD groove as in the prior art. The pin housing ID groove is modified to have a two-step groove comprising two adjacent regions having different depths (different diameters) and having a distinct transition lip therebetween. A spring clip of the correct size seats properly in the spring tower groove and in the lesser-diameter pin housing groove, resulting in a correct overall length of the SHVL. Any oversize clip is caught between the lower lip of the spring tower groove and the transition lip of the two-step pin housing groove, resulting in a SHVL distinctly shorter than nominal, which is easily detected by either direct length measurement or a gauge.

TECHNICAL FIELD

The present invention relates to hydraulic valve lifters for internalcombustion engines; more particularly, to a switchablevalve-deactivating hydraulic valve lifter having an external lost motionspring and spring tower; and most particularly, to an improvedarrangement for securing the spring tower to the pin housing thatindicates when mis-assembly has occurred.

BACKGROUND OF THE INVENTION

Hydraulic valve lifters that are specially equipped for selective lostmotion in an engine valvetrain to switchably deactivate an intake orexhaust valve are well known in the engine arts. In one form, such a“switchable hydraulic valve lifter” (SHVL) is provided with a lostmotion coil spring that is captured on an end of the SHVL body by aspring tower. The spring tower extends within the body to mate with apin housing that is slidably disposed within the body. When transverselocking pins in the pin housing are extended into engagement with thebody, the SHVL is rigid and acts to faithfully translate the rotarymotion of a cam lobe into reciprocal motion of an associated valve stem.When the locking pins are withdrawn into the pin housing, the cam lobecauses the pin housing to reciprocate within the body without suchtranslation (in “lost motion” of the cam lobe). That is, the body movesin a first direction responsive to the cam lobe, against the force ofthe lost motion spring while the pin housing remains stationary. Thus,the associated valve becomes “deactivated”.

During assembly of a SHVL, the spring tower enters the end of the pinhousing, the lost motion spring being in compression, and is retainedtherein by an expandable spring clip that is engaged in both an externalannular groove in the spring tower and an internal annular groove in thepin housing, the clip being captured between the two components.Assembling these components requires that the clip be expanded aroundthe spring tower (into the pin housing groove), allowing the springtower to pass through the spring clip. The clip then must snap into theannular groove of the spring tower and also lock into the groove of thepin housing when the compression of the spring is reduced. The annulargroove in the pin housing has a sloping side to accommodate slightvariations in clip diameter.

The prior art assembly just described is especially vulnerable tofailure from spring clips which are oversize. If the ID of the clip istoo large by as little as 0.15 mm, the clip may not fully lock into thetower groove, allowing spontaneous dis-assembly under use conditions inan engine, which is highly undesirable. Unfortunately, there is nosimple means at present for determining that this unsatisfctorycondition exists in any SHVL after assembly.

What is needed in the art is a means for recognizing, in a population ofmanufactured SHVLs, any SHVLs have been mis-assembled with anunacceptably large clip, to permit the faulty SHVLs to be segregated andreworked before being installed into engines.

It is a principal object of the present invention to permit simplerecognition of a mis-assembled SHVL.

SUMMARY OF THE INVENTION

Briefly described, an improved SHVL in accordance with the presentinvention includes an improved arrangement for locking a spring towerinto a pin housing. The spring tower is provided with an annular ODgroove as in the prior art. However, the pin housing ID groove ismodified to provide a two-step groove comprising two adjacent regionshaving different depths (different diameters) and having a distincttransition lip therebetween. An expansion clip of the correct size seatsproperly in the spring tower groove and in the lesser-diameter pinhousing groove, resulting in a secure mating and a correct overalllength of the SHVL. Any oversize expansion clip is caught between thelower lip of the spring tower groove and the transition lip of thetwo-step pin housing groove, resulting in a SHVL approximately 1.0 mmshorter than nominal, which is easily detected by either direct lengthmeasurement or a gauge.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is an elevational cross-sectional view of a portion of a priorart SHVL, substantially as shown in U.S. Pat. No. 6,866,014 B2;

FIG. 2 is a schematic cross-sectional view of a correctly-assembledprior art pin housing, spring tower, and expansion clip;

FIG. 3 is a schematic cross-sectional view of a mis-assembled prior artpin housing resulting from an expansion clip having an excessively largeID;

FIG. 4 is a schematic cross-sectional view of a correctly-assembled pinhousing, spring tower, and expansion clip in accordance with the presentinvention; and

FIG. 5 is a schematic cross-sectional view of a mis-assembled pinhousing in accordance with the present invention resulting from anexpansion clip having an excessively large ID.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplification set out hereinillustrates one preferred embodiment of the invention, in one form, andsuch exemplification is not to be construed as limiting the scope of theinvention in any manner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a prior art SHVL 10 comprises a body 12. A pinhousing 14 is slidably disposed in a first bore 15 in body 12 andretained therein by a spring seat 16 mounted on the end of body 12. Aplunger 18 and pushrod seat 17 are slidably disposed within a secondbore 19 in pin housing 14 for actuation by a conventionallash-adjustment mechanism (not appearing in the SHVL portion in FIG. 1).A lost-motion coil spring 20 is mounted on spring seat 16 and iscaptured by a spring tower 22 disposed within spring 20 and having aterminal flange 24. Spring tower 22 extends into second bore 19 and iscaptured therein by a tower-locking mechanism 26, the improvement ofwhich is the object of the present invention.

Referring to FIG. 2, a correct prior art tower-locking mechanism 26 isshown. Pin housing 14 is provided with an ID annular groove 28 having alower wall 30 orthogonal to second bore 19 and an upper wall 32 formedat an incline to second bore 19. Spring tower 22 is provided with an ODannular groove 34 configured similarly to pin housing groove 28. Anexpandable clip 36 is captured within both grooves 28,34, preventingspring tower 22 from being forced from second bore 19 by the expansiveforce of compressed lost-motion spring 20 (FIG. 1). To assemblemechanism 26, clip 36 is inserted into groove 28, then the nose 37 ofspring tower 22 is forced through clip 36, which is expanded therebyinto groove 28. Clip 36 slides along spring tower 22 until clip 36reaches and snaps radially inward into groove 34. Spring tower 22 thenis urged outwards of the SHVL by spring 20 until clip 36 also engageswall 32 of groove 28. The spring tower is thus correctly locked into thepin housing.

Referring to FIG. 3, it is seen that if the ID of an incorrect clip 36′is only slightly larger than nominal, clip 36′ cannot properly snap intogroove 34 and instead becomes trapped between wall 32 and the lowercorner 38 of groove 34. This is a metastable position that can allow theSHVL to appear to be locked correctly, yet under a load in useconditions in an engine 35, corner 38 may be forced past clip 36′ by aslight expansion of clip 36′ along wall 32, allowing the SHVL to becomecatastrophically dis-assembled. Thus, it is highly desirable to be ableto recognize when such mis-assembly has occurred, before installing amis-assembled SHVL into an engine 35.

Referring to FIG. 4, an improved tower-locking mechanism 126 inaccordance with the present invention is shown. Spring tower 22 issubstantially as shown in the prior art in FIGS. 1-3, comprising groove34, nose 37, and lower lip 38. However, pin housing 114 is modified suchthat ID annular groove 128 is a two-step groove having a first andgreater ID portion 128′, a second and lesser ID portion 128″, and atransition lip 140 therebetween. The difference between the inner andouter diameters of clip 36 (thickness of the clip itself) isapproximately equal to the difference between the diameters of groove 34and groove 128″. Thus, a correctly-sized clip 36 is trappedtherebetween, as shown in FIG. 4, resulting in a correct assemblysimilar to the prior art assembly shown in FIG. 1.

Referring now to FIG. 5, the benefit of the invention becomes obvious.Because groove 128 is provided in two steps 128′, 128″ having transitionlip 140 therebetween, oversize clip 36′ when mis-assembled into a SHVLcannot be seated in step 128″, in the correct fashion shown in FIG. 4.Rather, clip 36′ is trapped between lower lip 38 and transition lip 140,thus causing spring tower 22 to be axially displaced from its properlocation by a distance 142. This distance is equal to an overallshortening of the assembled SHVL. Judicious selection of the shapes andlengths of groove steps 128′, 128″ can amplify relatively small degreesof oversize of clip 36′ into relatively large values of distance 142.The resulting deviations of overall SHVL length from nominal are easilydetected by direct measurement or gauging, thus permitting sorting ofmis-assembled deactivating hydraulic valve lifters from a population ofdeactivating hydraulic valve lifters.

While the invention has been described by reference to various specificembodiments, it should be understood that numerous changes may be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedescribed embodiments, but will have full scope defined by the languageof the following claims.

1. A switchable hydraulic valve lifter for an internal combustionengine, comprising: a) a spring tower having an annular groove formed inan outer surface thereof; b) a pin housing having a bore for receivingsaid spring tower and having a two-step annular groove formed in aninner surface thereof; and c) an expansion clip disposed in said springtower annular groove and said pin housing two-step annular groove forlocking said spring tower into said pin housing bore, wherein saidtwo-step annular groove is defined by a first groove having a firstdiameter, a second groove adjacent said first groove and having a secondand larger diameter, wherein a correctly-sized expansion clip isaccepted into said spring tower annular groove and into said pin housingfirst groove, resulting in said switchable hydraulic valve lifter havinga first overall length, and wherein an oversized expansion clip isprevented from entering said pin housing first groove, resulting in saidswitchable hydraulic valve lifter having a second overall length.
 2. Aswitchable hydraulic valve lifter, in accordance with claim 1, whereinsaid two-step annular groove includes a transition lip formed betweensaid first and second grooves.
 3. A switchable hydraulic valve lifter,in accordance with claim 1, wherein said first overall length is greaterthan said second overall length.
 4. An internal combustion engine,comprising a switchable hydraulic valve lifter including a spring towerhaving an annular groove formed in an outer surface thereof, a pinhousing having a bore for receiving said spring tower and having atwo-step annular groove formed in an inner surface thereof, and anexpansion clip disposed in said spring tower annular groove and said pinhousing two-step annular groove for locking said spring tower into saidpin housing bore, wherein said two-step annular groove is defined by afirst groove having a first diameter, a second groove adjacent saidfirst groove and having a second and larger diameter, wherein acorrectly-sized expansion clip is accepted into said spring towerannular groove and into said pin housing first groove, resulting in saidswitchable hydraulic valve lifter having a first overall length, andwherein an oversized expansion clip is prevented from entering said pinhousing first groove, resulting in said switchable hydraulic valvelifter having a second overall length.
 5. A method for sortingmis-assembled switchable hydraulic valve lifters from a population ofswitchable deactivating hydraulic valve lifters, comprising the stepsof: a) establishing a predetermined correct overall length for acorrectly-assembled switchable hydraulic valve lifter; b) measuring theoverall length of each of said switchable hydraulic valve lifters; andc) segregating any switchable hydraulic valve lifters having an overalllength other than said predetermined correct overall length.